The long-term objectives of this proposal are to determine the molecular mechanism by which nonelectrolyte transport proteins function in the plasma membrane and are regulated by hormone action. The experiments described in this proposal have three major thrusts. The first is to determine whether insulin and glucocorticoids, two hormones with antagonistic effects on glucose transport in rat adipocytes, alter glucose transport activity by altering the number of transporters in the membrane or the activity of individual transporters. These experiments will utilize a cytochalasin B binding assay and a small unilammelar vesicle reconstitution techniques. The second thrust will use inhibitors of protein turnover to probe the role of regulators of protein turnover in modulating transport protein activity and as potential sites at which the activity of glucose transport is regulated by glucocorticoids. The third thrust is to identify any cytoplasmic or membrane-associated mediator of the glucocorticoid inhibition of transport. Studies will also be initiated to label and identify the insulin-sensitive transport protein or hormone-induced transport modulator by incorporating radioactive amino acids into adipocyte proteins in the presence and absence of glucocorticoids. The results of these experiments should provide a greater understanding of the mechanisms by which insulin, the body's primary regulator of glucose metabolism, and glucocorticoids, the body's primary antagonist to insulin action on glucose transport and a class of commonly prescribed pharmacologic agents, interact to regulate glucose transport and glucose metabolism in adipose tissue.